Osteoporosis: Diagnosis, Prevention and Treatment

By Thomas E. Menke, M.D.

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass and altered bone structure which leads to increased fragility of bones and susceptibility to fractures. The National Osteoporosis Foundation estimates that more than 10 million people in the United States have osteoporosis and an additional 19 million have low bone mass while not meeting criteria of osteoporosis.

Bone is a living matrix constantly remodeling in response to the mechanical stresses placed upon it and to the chemical/hormonal changes of the body. Bone mass increases during childhood, and peak bone mass is obtained on average by age 25. After this peak, bone loss occurs at a rate of 0.3% per year for men and 0.5% per year for women. The rate of bone loss increases to 2% - 3% per year at the onset of menopause.

The rate of bone turnover is dependent on the surface area of the ossified bone. Trabecular bone, which is found in the vertebra and the ends of long bones, has a much greater surface area than cortical bone. For this reason, osteoporosis causes the most significant bone density loss in trabecular bone. That is why fragility fractures most commonly occur in the spine, hip, and distal radius.

Risk factors for the development of osteoporosis include early menopause, prolonged periods of amenorrhea, poor nutrition, limited exercise, positive family history, a history of excessive alcohol intake and smoking. Bone marrow abnormalities, endocrinopathies, and long-term administration of corticosteroids can also lead to so-called “secondary osteoporosis.”

Diagnosis of osteoporosis is based on identifying patients with bone mineral density of 2.5 standard deviations less than the average value for healthy young adults. The study of choice for this assessment is dual-energy x-ray absorptiometry (a.k.a. DEXA scan). DEXA scan offers the best combination of precision, low radiation exposure, and affordability when compared with other available tests. Indications for performing a DEXA scan on a patient are still evolving, but include an assessment of risk factors, family history, and personal history of any fragility fractures.

Prevention is clearly the best solution to the problem of osteoporosis. Most people who develop osteoporosis likely never attained a normal bone mass as a young adult. Diet and exercise are the two most important reasons. Calcium requirements of 1,000 mg./day (up to 1,500-2,000 mg./day during pregnancy and lactation) are frequently not fulfilled. This can easily be corrected with diet changes or supplements.

Exercise, ideally in the form of brisk walking, is beneficial at all ages. In the extreme, however, it can be very detrimental. Extreme physical training in adolescent females is often associated with disordered eating and amenorrhea which leads to low bone mass. As a group, women who exercise and maintain normal menstrual cycles have the greatest bone mass. Eumenorrheic women who do not exercise have less bone mass, and amenorrheic women who exercise have the least. Female athletes who participate in gymnastics, diving, figure skating, dance, track, and synchronized swimming appear to be at the most risk.

Treatment for osteoporosis consists of exercise, most commonly in the form of a walking program, modification of the environment to reduce the risk of falls, and medications. Calcium supplements are beneficial only when a patient’s dietary intake is inadequate. Excess intake of calcium affords no benefit and can be harmful. Vitamin D deficiency occurs most commonly in strict vegetarians and in northern locations during the winter. A single high dose injection of Vitamin D in early winter has shown signs of being beneficial for these people.

Estrogen administration to postmenopausal women has clearly been shown to prevent bone loss and protect against fragility fractures. Side effects of periodic bleeding, and concern from increased risk of endometrial and breast cancer, has lead to acceptance of long-term use of estrogen by only one-third of those women started on it.

Calcitonin administered by injection and, more recently, intranasally is an alternative to estrogen therapy. In addition to maintenance of bone density, calcitonin has an analgesic property as a result of elevating levels of endorphins.

Bisphosphonates such as etidronate and alendronate work by directly inhibiting bone resorption, but can cause some indigestion.

Flouride decreases bone resorption, but has shown a dose related abnormality in bone mineralization which has limited its use.

Medications used to treat osteoporosis tend to cause multiple side effects. Their effectiveness is influenced by other disease processes and other medications. For these reasons, medical treatment of osteoporosis is generally managed by one’s primary care physician.

Fractures from osteoporosis cause significant morbidity. Hip fractures almost always require surgical treatment. Vertebral fractures usually respond to comfort measures of rest, bracing, and medications. New procedures (ie. vertebroplasty) are being developed to try to decrease the morbidity associated with vertebral fractures of moderate severity. Rarely, osteoporotic vertebral fractures require more aggressive surgical treatment.

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Last Updated:10/4/03